General Electric J85

The J85 was originally designed to power a large decoy missile, the McDonnell ADM-20 Quail. The Quail was designed to be released from a B-52 Stratofortress in-flight and fly for long distances in formation with the launch aircraft, multiplying the number of targets facing the SA-2 surface-to-air missile operators on the ground. This mission demanded a small engine that could nevertheless provide enough power to keep up with the jet bomber. Like the similar Armstrong Siddeley Viper being built in the UK, the engine on a Quail drone had no need to last for extended periods of time, so therefore could be built of low-quality materials.

The fit was a success on the Quail, but again like the Viper it was later built with normal grade materials and subsequently used to power small jet aircraft, including the Northrop T-38 Talon, Northrop F-5, Canadair CT-114 Tutor, and Cessna A-37 Dragonfly light attack aircraft. More recently, J85s have powered the Scaled Composites White Knight aircraft, the carrier for the Scaled Composites SpaceShipOne spacecraft, and the Me 262 Project.

The basic engine design is quite small, about 17.7 inches (45 cm) in diameter, and 45.4 inches (115 cm) long. It features an eight-stage axial-flow compressor powered by two turbine stages, and is capable of generating up to 2,100 lb_f (9.3 kN) of dry thrust, or more with an afterburner. At full throttle at sea level, this engine, without afterburner, consumes approximately 400 US gallons (1,500 L) of fuel per hour. At cruise altitude and power, it consumes approximately 100 US gal (380 L) per hour.

Several variants were produced.

The most advanced variant in the J85 series is the J85-21 model designed specifically for the F-5E/F during its development process.^[2]

The J85-21 design replaces AM 355 chromium nickel molybdenum stainless steel alloy, used by previous J85 models for compressor rotors and blades, with a titanium alloy. Its inlet diameter was increased from 17.7 in (45 cm) to 20.8 in (53 cm), and it included an added stage ahead of the base 8-stage compressor for a total of 9 stages. Its multiple disk rotors were replaced with a single-spool rotor, thus improving dry thrust to 3,600 lb_f (16 kN) and wet thrust to 5,000 lb_f (22 kN) while reducing mechanical complexity along with the weight gain of the J85-21 model.^[2]

More than 12,000 J85 engines had been built by the time production ended in 1988.^[3]

Thrust given in pound force (lbf) and kilonewtons (kN).

J85-GE-1

1,900–2,100 lb_f (8.5–9.3 kN)^[2]

J85-GE-2

2,850 lb_f (12.7 kN)

J85-GE-3

2,450 lb_f (10.9 kN)

J85-GE-4

2,950 lb_f (13.1 kN)

J85-GE-4A

2,950 lb_f (13.1 kN)

J85-GE-5

2,680 lb_f (11.9 kN) dry / 3,850 lb_f (17.1 kN) afterburning

J85-GE-5A

2,680 lb_f (11.9 kN) dry / 3,850 lb_f (17.1 kN) afterburning

J85-GE-7

2,450 lb_f (10.9 kN)

J85-GE-12

2,400 lb_f (11 kN)

J85-GE-13

2,720 lb_f (12.1 kN), dry / 4,080 lb_f (18.1 kN) afterburning^[10]

J85-GE-13A

License built for the Fiat G.91Y, 2,720 lb_f (12.1 kN) dry / 4,080 lb_f (18.1 kN) afterburning^[2]

J85-GE-15

2,925 lb_f (13.01 kN) dry / 4,300 lb_f (19 kN) afterburning^[2]

J85-CAN-15

Orenda manufactured J85-GE-15 for the Canadair CF-116, 2,925 lb_f (13.01 kN) dry / 4,300 lb_f (19 kN) afterburning^[2]

J85-GE-17

2,850 lb_f (12.7 kN)^[2]

J85-GE-17A

2,850 lb_f (12.7 kN)^[11]

J85-GE-17B

2,850 lb_f (12.7 kN)^[2]

J85-GE-17C

2,850 lb_f (12.7 kN)

J85-GE-19

3,015 lb_f (13.41 kN) dry

J85-GE-21A

3,500 lb_f (16 kN) dry / 5,000 lb_f (22 kN) afterburning^[10]

J85-GE-J1A

3,500 lb_f (16 kN) dry / 5,000 lb_f (22 kN) afterburning

J85-GE-J2

2,850 lb_f (12.7 kN)

J85-GE-J4

2,950 lb_f (13.1 kN)

J85-CAN-40

Manufactured by Orenda for the Canadair CT-114 Tutor, 2,650 lb_f (11.8 kN)^[2]

J85-GE-100

2,450 lb_f (10.9 kN)

• Bell X-14A/B
• Boom XB-1 demonstrator^[12]
• Canadair CT-114 Tutor
• Canadair CF-5
• Cessna A-37 Dragonfly
• HESA Yasin (without afterburner)
• HESA Kowsar (with afterburner)
• Fairchild C-123 Provider
• Fairchild AC-119K
• Fiat G.91Y
• Lockheed Have Blue
• Lockheed F-117 Nighthawk
• McDonnell ADM-20 Quail decoy missile
• North American Rockwell OV-10 Bronco - OV-10B(Z) target tug variant, the engine in addition to its turboprops^[13]
• North American T-2 Buckeye
• Northrop F-5
• Northrop T-38 Talon
• Republic AP-100
• Ryan MQM-34D Mod II target drone
• Ryan XV-5 Vertifan
• Saab 105Ö
• Scaled Composites White Knight

Data from ^{[17][18][19][20]}

Related development

• General Electric CJ610
• General Electric CF700

Comparable engines

• Armstrong Siddeley Viper
• Continental J69
• Fairchild J83
• Rolls-Royce Soar

Related lists

• List of aircraft engines